.main{
  width: 150px;
  height: 100px;
  border: 1px solid aqua;
  border-radius: 50%;
  position: relative;
  margin: 20px;
}
.ball{
  position: absolute;
  left: 50%;
  top: 50%;
}
p{
  width: 20px;
  height: 20px;
  margin: -50%;
  border-radius: 50%;
  background: aqua;
  animation: rotate ;
}